Fiber optic cables provide numerous advantages over traditional communication cables, particularly higher transmission speeds and improved transmission quality. However, fiber optic cable is susceptible to a unique problem associated with water accumulation around the cable. Installation of fiber optic cable typically involves burying conduit between two end locations. The fiber optic cable is then installed within the protective conduit. Water sometimes enters the conduit either through access points in the conduit or through condensation within the conduit. Either way, the water flows downhill and accumulates within the conduit. The conduit is usually buried below the frost line so that freezing does not occur. However, where the conduit is above the frost line and exposed to freezing temperatures, the water that has accumulated within the conduit freezes, creating significant pressure on the fiber optic cable within the conduit. This pressure can cause the fiber optic strands within the cable to bend, damaging the fragile glass strands that make up the fiber optic core and leading to signal degradation. Additionally, the force from the freezing ambient water can cause the glass strands that make up the fiber optic core to break, requiring costly repair. The problem is amplified when water penetrates the cable itself and freezes or when the glass fibers freeze.
Various solutions to these problems have been attempted. One solution is to fill the conduit with anti-freeze materials in an attempt to prevent water trapped inside from freezing. Another solution is to fill the conduit around access points with a material that expands within the conduit to create a barrier to water entry, forming a chemical plug. An additional solution is to drill weep holes in the conduit in an attempt to create drainage for trapped water. Invariably, due to elevation differences along the length of the conduit, plugged weep holes, or improperly trained personnel, these solutions have met with a limited amount of success. Additionally, chemical plugs can inhibit access to the cable and make cable removal and repair difficult.
While these methods attempt to prevent water from entering the protective conduit, it is desirable to prevent the displacement of the fiber optic core of the cable in the event that water does enter the conduit and freeze, applying a force directly to the cable. One available solution is to apply a jacket to the fiber optic cable that is made from a very robust material such as steel. In doing so, the force required to bend the steel jacket and displace the core would be greater than that created by the force of freezing water. However, this solution is expensive, hard to work with, and not designed for aqueous environments. Another solution for keeping water out of the fiber optic cable itself is to maintain positive air pressure within the cable. However, this solution does not prevent signal degradation due to forces from freezing water surrounding the cable within the protective conduit. For these reasons, a new method for minimizing signal degradation of fiber optic cable due to bending caused by the expansion of freezing ambient water is desirable. It is with respect to these considerations and others that the present invention has been made.